Capacitor anode
The application is that application number is dividing an application of 200980151003.2 applications, and application number is to be on December 7th, 2009 applying date of 2009801510032 applications.
The present invention relates to a kind of solid electrolyte capacitators anode, its preparation method based on NbO and the solid electrolyte capacitators with NbO anode.
Having the dielectric solid electrolyte capacitators of niobium pentoxide or tantalum pentoxide is widely used in electronics industry.It is based on form the niobium pentoxide of insulating barrier or the high dielectric constant of tantalum pentoxide in this class capacitor.The preparation of this anode is that the porous anode body by the finely divided porous agglomerate of tantalum-initial particulate or niobium-initial particulate is sintered into corresponding large surface is realized; wherein this agglomerate before sintering through being processed into the press body that shape is stable, then this press body high-altitude very at 1000-1500 ℃ through sintering 10-30 minutes.By electrolytic oxidation, on the surface of this sintered body (anode), produce pentoxide layer, its bed thickness is determined by the maximum voltage (forming voltage) of electrolytic oxidation again.This negative electrode can become the manganese nitrate dipping sponge kind structure of manganese dioxide to make or floods the structure of sponge kind and make or make with the polymeric dispersions of the polymer conducting electricity through polymerization reaction containing the electrolytical liquid precursor of thing with poly-through heat deflection by using.
In principle, the protoxide NbO of niobium
x, x=0.5-1.7 wherein, so can conductivity also be suitable as anode material because it is high.So recently proposed to replace Nb-metal or Ta-metal as the various suggestions of anode material with NbO.But NbO is unsuccessful because being so far as the commercial Application of anode material, and the capacitor being made by it has too high aftercurrent, and the anode integral body making by same procedure has extremely wide ratio aftercurrent to distribute.From many capacitor The book of Changes voltage breakdowns of a production batch, so that can not use.
The not good reason of capacitor performance with NbO-anode seems to be the defect sturcture being produced by preparation method: compare with Ta with ductile metal Nb, NbO is a kind of more crisp oxide ceramics, it produces open defect as being micro-crack when anode shaped, and these micro-cracks are also only not exclusively repaired when sintering.
Find, if before sintering being formed in without carrying out under pressure of this anode bodies, can not there is not this class defect.
Therefore the object of this invention is to provide a kind of for the NbO from presintering
x(x=0.5-1.7 wherein, preferred x=0.7-1.3) fine powder is prepared the method for solid electrolyte capacitators anode, and it passes through by powder forming anode base substrate, and this base substrate of sintering becomes anode bodies, the method is characterized in that, being formed in substantially of this base substrate do not complete under working pressure.
The present invention also aims to provide a kind of by anode bodies of the present invention and provide negative electrode to prepare the method for solid electrolyte capacitators for the anode bodies being shaped is provided.
By the first embodiment of the present invention, by NbO
x-powder suspension is in inert fluid, in preferred water, applied or be filled in plane or strike out on cochlear, little boat-shaped or barrel-shaped niobium metal paper tinsel or tantalum metal forming, by closely knit by means of ultrasonic vibration, dry and sintering.
Preferably by sedimentation, by rare suspended matter, apply NbO
x-powder.At this moment make niobium paper tinsel or tantalum paper tinsel bathe by suspension, so that powder deposition is on paper tinsel or deposit in said structure.Preferably use aqueous suspension thing.This NbO
xthe concentration of-powder should preferably be less than 50 g/l, is particularly preferably less than 10 g/l, more particularly preferably 2-8 g/l.To continuous charging in suspended matter, its reinforced amount is deposition and the amount of powder that draws off on paper tinsel.Through initial adjusting after date, in suspended matter, reach so particle size distribution, in suspended matter, just in time a kind of like this particle size distribution with the particle size distribution of the powder corresponding to being added deposits, so that does not substantially occur segregation effect.After drawing the paper tinsel applying by powder deposition, make this paper tinsel through ultrasonic unit, thus closely knit deposited powder bed.The wet powder layer drying that this is closely knit.Under aqueous suspension principle condition, dry the intensification of 150-180 ℃ through several hours rise to from 60-80 ℃ is preferred.
Preferably using average original particle size is 200-1000 nm, and more preferably the presintering powder of 400-800 nm (by the visual mensuration of REM-photo) is as NbO
x-powder.This secondary particle size (size of the initial particulate of sintering) is preferably 100-180 μ m (by Mastersizer with D50-pH-value determination pH; ASTM B 622).The secondary particle size of pressing Mastersizer distributes and preferably passes through D10=30-70 μ m, D50=100-180 μ m and D90=200-300 μ m definition.This secondary particulate can be spherical in shape or irregularly shaped.It is preferred that the irregularly shaped of piece stablized in deposition and the closely knit rear formation of ultrasonic wave.
By another embodiment of the present invention, by will be containing NbO
xthe creme of-powder is applied on niobium paper tinsel or tantalum paper tinsel and is shaped.
This method of preparing anode-base substrate is mentioned with screen cloth method for printing, template method for printing, ink-jet printed method and immersion forming process in relevant Nb-metal-anode technology and Ta-metal-anode technology, to produce thin type structure.A kind of claimed method for the preparation of capacitor-anode of US 3465426, prepares anode by the powder forming on paper tinsel in the method.
The claimed for example special creme to the refractory metal layer for the preparation of sintering of EP 1114430 B1.
The claimed anode for electrolyte-capacitor of EP 1208573 B1, wherein this anode bodies by can through solidify can continuous modification material form.
In this side's method, use the creme of being made by thin Nb-powder or Ta-powder and organic bond, this creme is applied in the substrate of being made by Nb-thin plate and Ta-thin plate and drying.Then pass through the first heat treatment to remove organic bond, then carry out sintering.
The shortcoming of this method is, when removing organic bond, carbon doping occurs in anode material.Although pass in time and update creme formula, also fail to make carbon content in capacitor lower than 150 ppm.But carbon is relevant with undesirable high leakage current.Therefore the method fails to obtain popularization in industry.
Find, in this class creme, use NbO
xwhen preparing capacitor ,-powder there is not carbon doping.Clearly, due to existing oxygen, when sintering, can remove carbon completely at the latest.
By this another embodiment of the present invention, be shaped by the creme containing organic bond is applied on the Nb-thin plate and Ta-thin plate that is plane, and by being heated to 150-550 ℃ to be dried this creme and to remove adhesive and carry out.
By means of creme shaping anode construction, preferably by template method for printing, undertaken.On the Nb-paper tinsel for this reason contacting at the anode that forms plane or Ta-paper tinsel, place the template of being furnished with spill figure, by means of scraper, creme is sent in the spill figure of this template.The spill figure of this template has the plane of required anode and extends shape, as two directions are the rectangle of several mm sizes.The thickness of this template has approximately predetermined the thickness of anode construction afterwards.This template thickness can be 50-500 μ m, is preferably 100-300 μ m.
The present invention also aims to provide the anode and the capacitor that are plane extension, wherein this anode is made by the sponge kind structure of the sintering of the protoxide (i.e. 0.5 < x < 1.7) of niobium, it has the anode that correspondingly plane is extended that is of being made by niobium and/or tantalum and touches face, wherein the carbon content in anode construction is less than 25 ppm, preferably be less than 15 ppm, be particularly preferably less than 10 ppm.
In addition, the present invention also aims to provide the solid electrolyte capacitators with above-mentioned anode, the ratio aftercurrent of this capacitor is less than 0.4 nA/ μ FV.
The creme that is particularly suitable for template method for printing is described below.
As adhesive, preferably use hydro carbons, special is that cellulose is as the hydroxypropyl cellulose of the Klucel H of ethyl cellulose N7, N20, N100, N200 or N300 or Hercules company, Klucel M or Klucel G type.Other applicable adhesive is polysaccharide, hemicellulose, acrylate, polyester-polyurethane, polyethers-polyurethane, urea-polyurethane, polyvinyl alcohol and its binary or multicomponent mixture.
According to compatibility, this adhesive is preferably dissolved in solvent as terpinol (Terpineol), and dihydroxylic alcohols is as ethylene glycol, 1,2-PD, butanediol, triethylene glycol, or in water, optionally at the temperature slightly improving.
In addition, in adhesive, also can add surface reactive material (wetting agent, antifoamer) as Surfinol 104 (Air Products company) or 2-[2-(2-methoxy ethoxy) ethyoxyl] acetic acid (Sigma-Aldrich company) or Byk 024 (BYK-Gardner company), and/or rheologic additive is as Rheolate 244 (Elementis Specialities company).
The spherical secondary powder that preferred use maximum particle size is 40 μ m is as NbOx-powder.Here, particularly preferred particle size distribution is D10=0.5-1.5 μ m, D50=1.5-3 μ m and D90=7-12 μ m.Average initial particle size can be 200-600 nm.
NbOx-powder is joined in adhesive composition, and with San Gun Shi Subcommittee-to grinding machine homogeneity.For being easy to soak, this powder can frontly in joining wetting agent solution be processed through suspending.Solid content in this creme also affects its viscosity.What it accounted for total ingredients is at least 70 and be up to 87 % by weight, is preferably 75-85 % by weight.
This creme is after homogeneity, at 10-50 s
-1shearing rate scan (rotary process) in the viscosity calculated with the flow curve that cone-plate measurement mechanism of 4o angle and 20 mm diameters records at 10 s
-1time be 80-100 Pas and at 50 s
-1time be that the creme of 3.5-10 Pas is specially adapted to template method for printing.In addition, creme of the present invention is characterised in that, with the component of elasticity of yield point, complex viscosity in linear viscoelasticity scope and viscous components and its decline degree or the rising degree (thixotropic behavior) when shear stress is cancelled characterize when applying shear stress rheological behavior, so regulate, to produce the surperficial anode enough with steep edge peace.
Yield point is tried to achieve under shear stress is controlled by plate-plate-geometry in the oscillation mode of 1 Hz of rheometer.If the component of elasticity of this complex viscosity no longer increases and decline with shear stress with shear stress is irrelevant, by definition, surpassed this yield point.The shear stress values of just in time determining yet this component of elasticity decline is stipulated as yield point.
At yield point place, the component of elasticity of the viscosity of creme of the present invention is 500-15000 Pas, is preferably 750-7500 Pas, is particularly preferably 1000-5000 Pas.Creme of the present invention is at least 0.5 times and maximum 1.5 times of component of elasticity of yield point place viscosity in the viscous components of yield point, preferably at least 0.75 times and maximum 1.25 times, and particularly preferably at least 0.9 times and maximum 1.1 times.
To the application in template is printed, the rheological behavior of this creme under shear stress and shear stress finish after (thixotropic behavior) quality of printing image is played a decisive role.By shear stress, reduced the structure that causes creme pseudoplasticity that its intensity is characterized by the component of elasticity of the viscosity at yield point place.In creme of the present invention, being that under the shear stress at 3 times, yield point place, this component of elasticity reduces by 50 %, preferably reduce by 75 %, particularly preferably reduce by 90 %.In the present invention, be under the shear stress of 3 times at yield point place, this viscous components drops to and is less than 5000 Pas, preferably drops to and is less than 1000 Pas, particularly preferably drops to and is less than 500Pas.
Shear stress drops to after the value at yield point place, forms again the structure of this creme.According to the present invention, after 5 seconds, form again (exceeding the component of elasticity of this viscosity before yield point) at least 25 % and the highest 90 %, preferably 50-80 % of this structure.According to the present invention, after shear stress is cancelled, it is the highest 10 times that the viscous components of this complex viscosity is that at least 1.25-of the component of elasticity of this complex viscosity doubly arrives, preferably 2-5 times.
To the space utilization of standard-capacitor geometry of rectangle, the steepness of this anode edge is important, therefore should be peaceful unslow.Very steep edge as the edge conventionally producing when anode suppress be imperfect because the passivation at this edge and apply and cause there be additional expending (as so-called core-shell-passivation).
The dimensionless of steepness that starts the point obviously rising at anode from thin plate plane and at least reach the edge of the anode that height that the distance S measuring perpendicular to edge between the point of average anode end face height H (being normalized to the high H of average anode end face) is defined as the printing on flat thin plate is H is measured M.
This dimensionless is measured H/S corresponding to the average gradient at this edge.If this is measured is that average gradient is 1, distance is just in time equally long with anode height.If this is measured is 2, distance is just in time half length that anode is high.To vertical edge, this is measured without definition or " unlimited ".
Because the profile at this edge is measured with the limited step pitch s of laser-profilometer, so measuring, this is H/s to the maximum.All edges with the steepness between " unlimited " and H/s obtain same H/s so the undistinguishable measured of institute's dispensing.
S should so select, so that H/s is at least 5.
For evaluating whole border width and flattening numerical value, disperse (Streuungen), along this edge, will measure the height of at least 20 positions, and try to achieve arithmetic mean.
In anode situation of the present invention, this nondimensional M of measuring value is 0.5-4.5, preferably 1-4.5, particularly preferably 2.5-4.5.
With accompanying drawing in detail the present invention is described in detail below.
Brief description
Fig. 1 illustrates the cross section that is suitable for the niobium-paper tinsel of deposition formation method or the anode contact structures with spill figure of tantalum-paper tinsel;
Fig. 2 illustrates the structure of Fig. 1 of preferred use;
Fig. 3 schematically shows the equipment vertical view that is suitable for deposition formation method;
Fig. 4 illustrates the A-A cross section of Fig. 3 equipment;
Fig. 5 illustrates the B-B cross section of Fig. 4 equipment;
Fig. 6 illustrates the profiler scanning curve in the creme coating of preparing by template stamped method;
That Fig. 7 is illustrated in that 20 measurement point positions calculate and normalize to the boundary curve of average anode end face height and the edge steepness of the anode of the present invention of calculating thus;
That Fig. 8 is illustrated in that 20 measurement point positions calculate and normalize to the boundary curve of average anode end face height and the edge steepness of the counter electrode calculated thus.
In Figure 4 and 5, unless separately indicated in literary composition, cross section represents to be represented by fine rule with visible light by thick line.
As shown in Figure 1, at the niobium-paper tinsel for deposition formation method or tantalum-paper tinsel 1, form preferred zigzag spill figure 5, consequently form the tactile face 2 of anode and contact bonding jumper (steg) 3 with anode, it interconnects through main bonding jumper 4.Therefore paper tinsel can have and is greater than 100, and preferably 1000 and more anode contact-making surface 2.This spill figure 5 can produce by punching press or laser cutting.The size all directions of this anode contact-making surface 5 can be several mm.For preventing on bonding jumper 3 deposition, as shown in the cross section in Fig. 2, these bonding jumpers at the link position place with main bonding jumper 4 and with the link position place bending of anode contact-making surface 2, so that this bonding jumper 3 projection vertically upward.Mark 6 means the NbO of deposition on anode contact-making surface 2
x-powder bed.Mark 7 means this powder and also on main bonding jumper, deposits.If the main bonding jumper 4 of bending, as shown in Fig. 2 is right-hand, can prevent this deposition substantially.In the indicative icon of Fig. 1 and 2, this anode contact-making surface is plane.But this anode contact-making surface also can form the spill of spoon class or have the box-like of periphery.Therefore, this for example rectangular anode contact-making surface also can be in the form of a ring or ellipticity or other shape.
For implementing the equipment 1 of this deposition formation method, be shown in Fig. 3-5.This equipment consists of the container of two intersections, in its crosspoint, is deposition vessel 2.The paper tinsel representing with lowercase is by one of this container (paper tinsel is through container), and wherein this paper tinsel occupies position a successively by the moving direction shown in arrow respectively, b, c, d and e (Fig. 4).The paper tinsel for example with Fig. 2 structure is sent at a place, at b place, introduce in chamber 3 and be deposited under liquid level 12, then at c the outlet in deposition vessel below by, form thus sedimentary deposit, at d place, draw in chamber 4 and rise on liquid level 12, and at e place, be sent to closely knit, the dry and sintering of unshowned ultrasonic wave.
Meeting at right angles (Fig. 5) in another container of configuration with the first container, in the flowing space 5, with blender 10, make to contain NbO
xthe suspended matter of-powder adds with pump as shown in crooked arrow around sedimentation container 2.This powder particulate sinks in the flow of suspension of these deposition vessel 2 tops, and enters in the deposition vessel of being furnished with fixed network grid 13 2 of opening wide above.The powder feeding continuously through fresh powdering inlet 6, its amount equates with the amount of powder being gone out by foil.The powder of sedimentation returns in suspended matter through suspended matter conduit 7 at these container bottom 8 places again.
Paper tinsel separates (Fig. 4) by the shielding 9 of angle type with suspended matter circulation vessel 5 through container 3,4, and wherein the lower edge in shielding 9 provides passage 11, by this passage, the powder not being deposited on paper tinsel can be entered in suspended matter torus 5 again.
By embodiment below in detail the present invention is described in detail.
Embodiment
Embodiment 1:
Use formula is NbO
1.07bET-surface be 1.24 m
2/ g and particle size distribution be corresponding to D10=33 μ m, D50=107 μ m, and the random powder of protoxide of the niobium of D90=286 μ m.This powder is comprised of the initial particulate of sintering, and this fine particle diameter is about 620 nm by the visual mensuration of REM-photo.
This powder is dispersed on the surface of the glass container that is full of the water that contains a small amount of wetting agent.In the bottom that approaches this container, its of corresponding Fig. 2 structure is thick is 70 μ m, and having 64 sizes is 6x6 mm
2the niobium paper tinsel of anode contact-making surface remain on the turning arm below lid.After 15 minutes, rotate this paper tinsel, so that it is no longer by cap covers.On this anode contact-making surface, deposition is had an appointment after the thick powder bed of 0.5 mm, and this paper tinsel is rotated to below lid again.At this moment no longer including powder is dispersed on water surface.After the powder deposition being also dispersed in water, this paper tinsel is taken out, and be placed on by ultrasonic wave quartz and cause 30 seconds on the plate of vertical vibration.Then, first this paper tinsel through coating is dried 4 hours in drying oven at 60 ℃, then at 80 ℃, is dried 4 hours again, finally at 120 ℃, is dried 4 hours again.The paper tinsel of this drying is introduced in high vacuum sintering furnace again, after to stove evacuation, made furnace temperature in l hour, be raised to 1400 ℃, at this temperature, keep again 15 minutes.Follow cool to room temperature.
The protoxide layer of the niobium of the slightly thick porous that is coated with secure adhesion above of this anode contact-making surface.The weightening finish of this paper tinsel is 4.03 g, and the counterpoise of anode (coating of anode contact-making surface) is 63 mg.
For the characteristic of check capacitor, the paper tinsel that this is had to 64 anodes immerses in the phosphoric acid of 0.1 % by weight downwards, thus bonding jumper 3 (Fig. 2) part remain on acid surfaces above.Be limited under the current strength of 300 mA, be shaped to the shaping voltage of many 30 V, current strength drops at 0 o'clock and also keeps this voltage 2 hours.
Phosphoric acid with respect to 0.1 % by weight carries out aftercurrent measurement as negative electrode.With respect to the sulfuric acid of 18 % by weight, as negative electrode, in 10 V bias voltages and frequency, be to carry out capacitance measurement under the alternating voltage of 120 Hz.The ratio electric capacity of trying to achieve through 64 anodes is 148380 μ FV/g, and the aftercurrent of trying to achieve is 0.43 nA/ μ FV.
Embodiment 2
Use formula is NbO
0.95specific area be 0.76 m
2/ g and particle size distribution be corresponding to D10=0.85 μ m, D50=2.0 μ m, the protoxide powder of the niobium of D90=8.0 μ m and D100=36.2 μ m.
By mixing following ingredients, prepare creme:
The adhesive of 14.3 % by weight, it contains the ethyl cellulose N7 in terpinol of 5 % by weight,
The MEEE of 0.5 % by weight as wetting agent and
The Nb of 85.2 % by weight
x-powder
And then homogenizing in San Gun Shi Subcommittee-to grinding machine.By at 10-50 s
-1shearing rate scan (rotary process) in the flow curve of cone-plate measurement mechanism record of 4o angle and 20 mm diameters, the viscosity of the creme that this micro-touch becomes is at 10 s
-1time be 90 Pas and at 50 s
-1time be 5.2 Pas.
With this creme, adopt and have 108 4.6x4.6 mm
2the thick Stainless Molding Board of 150 μ m of spill figure in semi-automation, print that on crowd EKRA M2, to print 3 its sizes be 10x10 cm
2with thickness be the niobium paper tinsel (embodiment 2a, 2b, 2c) of 70 μ m, this spill figure is 6 way double-lines rows of every 18 spill figures.Use the rubber scraper coating that Shore hardness is 90.Scraper pressure and scraper speed and the creme amount being coated with on paper tinsel are as follows:
Embodiment 2a:50N, 60 mm/s, 0.997 g
Embodiment 2b:70N, 80 mm/s, 0.946 g
Embodiment 2c:30N, 40 mm/s, 1.061 g
This paper tinsel through printing is dried l hour in drying by circulating air case at 80 ℃.The structure of drying is carried out geometry by means of laser profile measuring instrument and is characterized.Fig. 6 illustrates the thickness distribution of the dry creme printing of embodiment 2b.On the direction of propulsion of scraper, produce thickness a little and increase (in Fig. 6 right-hand).
This dry printing paper tinsel is removed adhesive and sintering with following heating curves in high temperature-high pressure-stove:
From room temperature to 350 ℃: 25 K/min,
At 350 ℃: keep 15 minutes,
From 350 ℃ to 800 ℃: 25 K/min,
From 800 ℃ to 1050 ℃: 5 K/min,
From 1050 ℃ to final temperature: 25 K/min, and
In final temperature, keep 15 min.
Every paper tinsel, at 1300 ℃, is detained 1440 ℃ (final temperatures) lower sintering for 1370 ℃.The adhesion of this anode on all paper tinsels is all good.Make paper tinsel collision table edge can confirm no crack.
The anode of arranging on paper tinsel separates by saw (sawing wide 45-NIR (S)), as embodiment 1 its capacitor specific characteristics of check.Mean value as every 10 anodes obtains lower train value:
Embodiment 2a:83687 μ FV/g, 0.203 nA/ μ FV,
Embodiment 2b:75506 μ FV/g, 0.158 nA/ μ FV,
Embodiment 2c:94620 μ FV/g, 0.386 nA/ μ FV.
Carbon content in all anodes, all lower than 15 ppm, more specifically, is 4-6.4 ppm in the anode of embodiment 2a, is 5.2-7.3ppm and in the anode of embodiment 2c, is 3.7-5.8ppm in the anode of embodiment 2b.